The ultrastructure of the preformed ecdysial 'line of weakness' in the puparium cap of Elenchus tenuicornis (Kirby) (Insecta: Strepsiptera).

This study describes the ultrastructure at 'the line of weakness' in the male puparium of Elenchus tenuicornis (Kirby) (Insecta: Strepsiptera). Superficially this line looked like an area of untanned cuticle but ultrastructurally it had an undifferentiated epicuticle, an untanned exocuticle and a loose textured endocuticle. It is speculated that the E. tenuicornis pharate adult male prior to emergence smears a chemical solution on the inner rim of the 'line of weakness' which dissolves the exo- and endocuticles. Following this, the slightest pressure exerted by the ptilinum of the male breaks open the cap of the puparium.     

Morphology of the female Myrmecolacidae (Strepsiptera) including the apron, and an associated structure analogous to the peritrophic matrix

Development in the totally endoparasitic female Strepsiptera has been clarified by light and electron microscopy. At the end of the 4th instar the cuticle sclerotizes anteriorly to form the cephalothorax and collar, the former of which is later extruded through the host cuticle. Posteriorly, the cuticle remains unsclerotized, and this region is within the host. The moult to the neotenic adult takes place within the 4th instar cuticle, and the epicuticles of the previous instars are retained as persistent sheaths. The gut, which is present in the earlier endoparasitic stages, is lost after extrusion of the cephalothorax, and a novel structure develops on the ventral surface of the neotenic female. Due to the position of this novel structure in the neotenic female, this area is called an apron. The detailed structure of the membranes in the apron in Stichotrema dallatorreanum Hofeneder from Oro Province, and of another female myrmecolacid (which has a different host) from West New Britain in Papua New Guinea, is described. A dual function for the apron is proposed.     

The ultrastructure of the preformed ecdysial ‘line of weakness' in the puparium cap of Elenchus tenuicornis (Kirby) (Insecta: Strepsiptera).

This study describes the ultrastructure at ‘the line of weakness’ in the male puparium of Elenchus tenuicornis (Kirby) (Insecta: Strepsiptera). Superficially this line looked like an area of untanned cuticle but ultrastructurally it had an undifferentiated epicuticle, an untanned exocuticle and a loose textured endocuticle. It is speculated that the E. tenuicornis pharate adult male prior to emergence smears a chemical solution on the inner rim of the ‘line of weakness’ which dissolves the exo- and endocuticles. Following this, the slightest pressure exerted by the ptilinum of the male breaks open the cap of the puparium.     

Review of the Order Strepsiptera

The morphology, biology and life history of the immature stages, the free-living and the neotenic females (of the suborders Mengenillidia and Stylopidia respectively) and the free-living males of the order Strepsiptera are discussed. Strepsiptera are entomophagous parasitoids and are known to parasitize seven orders and thirty-five families of Insecta. The morphological and physiological changes they cause to the host insect are outlined. The classification of the order is revised; the geographical distribution, phylogenetic system and keys to the families, subfamilies and genera (when possible) are given. As the sexes are dimorphic, separate keys are provided for adult males and neotenic females.     

Apolysis without ecdysis in larval development of a strepsipteran, Elenchus tenuicornis (Kirby)

Previous uncertainty concerning the number of larval stages in a strepsipteran ( Elenchus tenuicornis ) was resolved by transmission and scanning electron microscope observations. The first larval instar (triungulinid) is free-living: after entering the host (a delphacid) it undergoes a normal ecdysis. The resulting second instar larva undergoes two further apolyses without ecdysis. In the male, the cuticle of the fourth instar larva tans to form the puparium, while the female becomes sexually mature without a further moult after extrusion of the cephalothorax through the host cuticle. The discarded exuviae of the triungulinid remain in the host abdomen; subsequent larval staging is made possible by the retention of the exuviae ensheathing the larva as each apolysis is accomplished.     

The effects of stylopisation on the sexual development of Javesella dubia (Kirschbaum) (Homoptera: Delphacidae)

This is the first record of the entomophagous parasite Elenchus tenuicornis (Kirby) parasitizing Javesella dubia (Kirschbaum) in England. The effects of E. tenuicornis on the development of (a) the primary, secondary and tertiary sexual organs, and (b) the body characters of J. dubia are discussed in detail.